P1647: CONTRIBUTION OF NEXT GENERATION FLOW (NGF) CYTOMETRY IN PRIMARY IMMUNE THROMBOCYTOPENIA (ITP): UTILITY FOR THE DIFFERENTIAL DIAGNOSIS WITH MYELODYSPLASTIC SYNDROMES
Authors: T. J. Gonzalez-Lopez, S. Matarraz, I. Caparros, M. F. Lopez-Fernandez, M. E. Mingot-Castellano, A. Jimenez Martin, F. Fernandez-Fuertes, J. I. Sánchez Gallego, P. Leoz, B. Cuevas Ruiz, M. V. Cuevas Ruiz, C. Martin Marín, J. Olazabal Herrero, P. de Vicente Cámara, A. Orfao
Journal: HemaSphere (2022)

Background: Primary immune thrombocytopenia (ITP) is an immune-mediated acquired disorder characterized by impaired production and increased destruction of platelets with an elevated risk of bleeding. At present, diagnosis of primary ITP still remains one of exclusion with a need to discard other causes of isolated thrombocytopenia, in the absence of robust and accurate clinical and laboratory diagnostic criteria. For the diagnosis of ITP, a bone marrow (BM) study may be useful to differentiate between ITP and other diseases, such as myelodysplastic syndromes (MDS). Next generation flow (NGF) has emerged as a potential useful tool in these settings. Aims: In FCR-PTI-2017-01 study we prospectively evaluated the potential utility of NGF analysis of BM for more accurate diagnosis of ITP vs MDS. Methods: Multicenter, prospective, Spanish study to investigate morphological and/or immunophenotypic profiles among BM cell compartments from patients ≥ 18 years with newly diagnosed ITP or MDS. A multiparameter characterization of multiple compartments of BM cells was performed using the 8-color panel designed and validated by the EuroFlow Consortium for the diagnosis and characterization of MDS and acute myeloid leukaemia. NGF BM blinded results were then compared with the BM cytomorphological diagnosis. Results: 62 patients, median age 71 years, 59% male, were included. Main comorbidities were neoplasms (19%), diabetes (17%), chronic respiratory disease (12%) and cardiac insufficiency (10%). Median platelet count at diagnosis was 45 x 109/µL (range: 4-98 x 109/µL) and 20.6% of patients had bleeding at diagnosis. By cytomorphology, expert hematologists were able to conclude an ITP or MDS diagnosis in only 31 cases of the 53 samples that could be analyzed (58.5%) [ITP (n=18), MDS (n=10) or inconclusive, i.e. unclassifiable, (n= 25)]. 62 BM samples evaluated by NGF were allocated in 4 immunophenotypic groups attending to: maturation blockades, abnormal antigen expression and cross lineage markers. We observed normal phenotype cases (n=10), isolated (unilineage) alterations (n=24), mild multilineage (>1) alterations (n=20) and severe multilineage (MDS-like) phenotypes (n=8). Cytomorphology diagnosed our cases as ITP, MDS or unclassifiable with a median number of alterations observed by BM NGF of 4 (IQR, 3-6), 2 (IQR, 1-6) and 4 (IQR, 3-5) respectively. For ITP cytomorphology group, NGF demonstrated numerous BM alterations being monocytic alterations (n=17, 94%) the most frequent finding observed. MDS presumed cases were also associated with monocytic alterations (n=5, 50%) with a frequent decrease in neutrophil precursors (n=4, 40%). On the contrary, when cytomorphology was not capable to establish a diagnosis, NGF showed a mixture of alterations with no clear predominance of none of them (Table 1). Image:Summary/Conclusion: Limitations of BM cytomorphology when facing an isolated thrombocytopenia were demonstrated here. However, normal or unilineage BM NGF alterations may lead us to an ITP diagnosis while mild or severe multilineage BM phenotypes may correlate good with MDS.